1. Field of the Invention
The invention relates to a method and apparatus for aerial spraying of agricultural chemicals.
2. Description of the Prior Art
Several United States patents exist that are known to have relevance to aerial electrostatic spraying (i.e., U.S. Pat. Nos.: 4,004,733; 4,328,940; 4,703,891; 4,560,107; and 5,042,723). It is an experimental fact that electrostatically charged sprays do not show depositional enhancement upon crops until the associated spray charge-to-mass ratio exceeds 0.8 millicoulomb/kilogram, symbolically: (Q/M.gtoreq.0.8 mC/kg) (Law and Lane, 1981, ibid). Accordingly, if this ratio is elevated to Q/M=1.0 mC/kg, then there would be an expected depositional advantage of 1.0/0.8=1.25 or 25% by using the higher (Q/M=1.0) charge level. However, aerial sprays labeled for agricultural use are not directly chargeable with conventional nozzles. Specifically, there are currently no known commercial or patented nozzles capable of meeting the requirements of a practical, aerial, electrostatic spray-charging nozzle.
Research has shown however that if these foregoing problems can be overcome, biological efficacy can be obtained with less aerial sprayed chemicals than are currently used. Some examples of recent research document this Carlton et al. (1995b, Cotton pesticide deposition from aerial electrostatic charged sprays, ASAE Paper No. AA95-007, ASAE, St. Joseph, Mich.) showed that an aerial spray charging level of Q/M=.+-.1.15 mC/kg significantly increased deposition on cotton over that of one where Q/M=.+-.0.80 mC/kg. Latheef et al. (1995, Aerial electrostatic charged sprays for control of sweetpotato whitefly in cotton, ASAE Paper No. AA95-008, ASAE, St. Joseph, Mich.) showed that whiteflies were controlled significantly better using a charged spray (Q/M=.+-.1.15 mC/kg) than the conventional sprayed cotton. The charged spray achieved this result using 1/10 the volume of water carrier as the conventional aerial spray while both sprays contained the same amount of active ingredient. Carlton et al. (1995a, ibid) also has shown that a bipolar charged spray of Q/M=.+-.2.64 mC/kg resulted in a deposition on cotton that was 4.3 times greater than the uncharged counterpart. These data show that by properly controlling the spray charging process, deposition can be enhanced while resulting in efficacy.